Kramer in U.S. Pat. No. 3,672,577 discloses a grid plate assembly for a fluid bed reactor including an apertured grid plate having nozzle elements in the apertures. The apertures and nozzle elements are structured to prevent dislodgment of the nozzle elements from the grid plate during use of the assembly and yet permit ready removable of the nozzle elements from the apertures when desired.
Dalton in U.S. Pat. No. 2,841,476 discloses a gas liquid contacting apparatus having a chamber, a horizontally disposed apertured plate in the chamber, a mass of finely divided solids supported on the plate and adapted to subside thereon when non-fluidized, and means of passing fluidizing gases through the apertures to fluidize the solids and gas introduction means adapted to limit passage of the solids into the apertures when the solids are subsided. The gas introduction means having an insert in each aperture. The insert having a tubular hollow member extending upwardly from the aperture. The member being open at the bottom and closed at the top and having sidewalls of substantial thickness.